Unusual human rotavirus strains having subgroup I specificity and "long" RNA electropherotype

During an epidemiological study of human rotavirus in Metro Manila, Philippines, we found 20 unusual strains which belong to subgroup I but have "long" RNA pattern typical of subgroup II human rotavirus. The RNA patterns of the 20 strains were classified into four groups though they were very similar to each other. Four strains, designated L4, L26, L27, and L34 were isolated in MA104 cells from stool specimens. They possessed subgroup I specificity and long RNA pattern identical to that of the viruses in the original stool samples. The serotype specificity of these strains could not be determined by either enzyme-linked immunosorbent assay (ELISA) or neutralization test, while one strain (L27) was neutralized by serotype 2-specific anti-VP4 monoclonal antibody. These strains were suggested to have an unusual antigenicity on VP7.